[v4,0/5] Negotiate the NIC's ability to deliver Rx metadata to the PMD

  In 2019, commit [1] announced changes in DEV_RX_OFFLOAD namespace
intending to add new flags, RSS_HASH and FLOW_MARK. Since then,
only the former has been added. The issue has not been solved.
Applications still assume that metadata features always work
and do not need to be configured in advance.

The team behind net/sfc driver has given this problem more thought.
Conclusions that have been reached are as follows.

1. Not all kinds of metadata can be represented by device offload flags.
   For instance, having flag RSS_HASH is legitimate because the NIC is
   supposed to actually compute something when this feature is active.
   However, if similar flag existed for Rx mark, requesting it would
   not make the NIC actually compute anything. The HW needs external
   stimuli (flow rules) in order to set the mark in the first place.

2. As a consequence of (1), it is apparent that the user's ability to
   use Rx metadata features is complex and consists of multiple parts:
   a) the NIC's ability to conduct the flow actions (set metadata);
   b) the NIC's ability to deliver metadata (if set) to the PMD;
   c) the PMD's ability to provide metadata received from the
      NIC to the user by virtue of filling out mbuf fields.

3. Aspects (2-a) and (2-c) are already addressed by flow validate API
   and the procedure of dynamic mbuf field registration respectively,
   hence, the only problem which really needs a solution is (2-b).
  
Patch [1/5] of this series adds a generic API to let the application
negotiate the NIC's ability to deliver specific kinds of metadata to
the PMD. This API is supposed to be invoked during initialisation
period in order to let the PMD configure HW resources which might
be hard to (re-)configure in the adapter's started state without
causing traffic disruption and other unwanted consequences.

[1] c5b2e78d1172 ("doc: announce ethdev API changes in offload flags")

Changes in v2:
* [1/5] has review notes from Jerin Jacob applied and the ack from Ray Kinsella added
* [2/5] has minor adjustments incorporated to follow changes in [1/5]

Changes in v3:
* [1/5] through [5/5] have review notes from Andy Moreton applied (mostly rewording)
* [1/5] has the ack from Jerin Jacob added

Changes in v4:
* [1/5] has the API contract clarified to address concerns raised by Ori Kam
* [1/5] has the API name fixed to use term "metadata" instead of "meta"
* [1/5] has testpmd loglevel changed as per the note by Ajit Khaparde
* [1/5] has testpmd code revisited to take multi-process into account
* [2/5] through [5/5] have the corresponding adjustments incorporated

Ivan Malov (5):
  ethdev: negotiate delivery of packet metadata from HW to PMD
  net/sfc: support API to negotiate delivery of Rx metadata
  net/sfc: support flow mark delivery on EF100 native datapath
  common/sfc_efx/base: add RxQ flag to use Rx prefix user flag
  net/sfc: report user flag on EF100 native datapath

 app/test-flow-perf/main.c              | 21 ++++++++++
 app/test-pmd/testpmd.c                 | 37 ++++++++++++++++++
 doc/guides/rel_notes/release_21_11.rst |  9 +++++
 drivers/common/sfc_efx/base/ef10_rx.c  | 54 ++++++++++++++++----------
 drivers/common/sfc_efx/base/efx.h      |  4 ++
 drivers/common/sfc_efx/base/rhead_rx.c |  3 ++
 drivers/net/sfc/sfc.h                  |  2 +
 drivers/net/sfc/sfc_ef100_rx.c         | 19 +++++++++
 drivers/net/sfc/sfc_ethdev.c           | 29 ++++++++++++++
 drivers/net/sfc/sfc_flow.c             | 13 +++++++
 drivers/net/sfc/sfc_mae.c              | 22 ++++++++++-
 drivers/net/sfc/sfc_rx.c               |  6 +++
 lib/ethdev/ethdev_driver.h             | 22 +++++++++++
 lib/ethdev/rte_ethdev.c                | 25 ++++++++++++
 lib/ethdev/rte_ethdev.h                | 53 +++++++++++++++++++++++++
 lib/ethdev/rte_flow.h                  | 12 ++++++
 lib/ethdev/version.map                 |  3 ++
 17 files changed, 311 insertions(+), 23 deletions(-)